BOO?!...MORE LIKE BOO-HOO! “American Idol” ratings are sooo bad that even “PHYLLIS,” the show’s legendary female ghost-in-residence – famed for wooing hunky male judges or contestants, and jealously haunting/harassing the gals with her scary pranks – has abruptly vanished from the set!

“She’s apparently off looking for more popular shows to haunt,” said a show insider, citing the whopping 22 percent drop in “Idol” ratings – plus a 23 percent loss of audience in the advertiser-desired 18-49 demographic! “Phyllis has been lurking around backstage for years, but she’s been a no-show all season,” said the source.

Show staffers recalled with near-nostalgia the time Phyllis got jealous of a female stage manager who got too cozy with RYAN SEACREST – and the woman ended up in the hospital after a huge tower mysteriously crashed down near her, spraying glass everywhere.

But for one brief moment recently, cast and crew started gasping: “Phyllis?” – when a huge chandelier that had just been hung over­head suddenly started moving mysteriously. “The fixture kept swaying for no reason, and no one wanted to get near it,” said the source.

“Everyone was scared Phyllis could be up to her old tricks – and Ryan Seacrest flat-out refused to stand under that chandelier.” But nothing happened, the swaying finally stopped, and staffers cracked that their green-eyed ghost has gone on to greener pastures – just like “American Idol” viewers!